1. Topic A.3 – Perception of stimuli

2. Receptors detect changes in the environment. Each organ in your body has some amount of receptors, but sensory organs have a high amount of these receptors. The major three sensory organs are: The Eye The EarThe Nose Each of these organs have different receptors, specifically tuned to receive signals from a certain material from our environments. They also each have a particular region of the brain that they work with to process information as a part of sensation. The four types of receptors are: Mechanoreceptors Thermoreceptors Photoreceptors Chemoreceptors

3. Rods and cones are photoreceptors located in the retina. These photoreceptors receive different types of light: Rods work with low light, while cones deal with bright light. These two types of cells work together so we can see in all conditions. Draw this diagram of the eye, then try and draw it again from memory – do you seem to be better at remembering the colored parts?

4. Bipolar cells send the impulses from rods and cones to ganglion cells, which transmit them to the brain via the optic nerve. The axons of the ganglion cells form the optic nerve, which transmits information from the eye to the brain. Steps of the vision pathway are: -Rods and cones receive the light stimulus. -Rods and cones synapse with the bipolar neuron. -The bipolar neuron carries the impulse to the ganglion cell. -Ganglion cell is located in the optic nerve. -The optic nerve carries the impulse to the brain. In red-green colorblindness, the rods that specifically receive the red and green wavelengths of light are blended into one type of photoreceptive cell, leading to dichromatic vision

5. Structures in the middle ear transmit and amplify sound. How is sound perceived by the ear? Bones in the middle ear – the malleus, incus and stapes, all receive vibrations from the tympanic membrane (eardrum) and multiply them approximately 20 times Stapes strikes the oval window to vibrate Vibration passed to the fluid in the cochlea Hair cells (specialized form of mechanoreceptors, release NTs across a synapse to the auditory nerve Stimulation of sensory neuron, and conveyance to brain for processing of sound processing. Try and draw this diagram from memory. How many parts can you remember?

6. Sensory hairs of the cochlea detect sounds of specific length. The hair cells of the cochlea are mechanoreceptors that each detect a specific wavelength of sound. When a sound that they resonate with is heard, they vibrate and a specific message is sent to the brain about the type of sound that is heard. If these hair cells vibrate too severely, or for too long, they can become worn out, or damaged. And these hair cells do not grow back. It is the bending or breaking of these hair cells that can send random nerve impulses to the brain, leading to a constant sound – known as Tinnitus. This can lead to hearing loss of certain frequencies of sounds as you age.

7. Detection of chemicals in the air occurs by the many different olfactory receptors. The chemoreceptors in the nose are what allow us to receive the plethora of smells that we can smell, almost 10,000! People that lack certain genes, lack the ability to make these chemoreceptors do not have the ability to smell different things, such as digested asparagus. Shifts in the available chemoreceptors can lead to a variety of disorders in the family –osmias. Anosmia, Hyposmia, Parosmia, Phantosmia What do you think these disorders do by their stems?

8. Neuropharmacology Inquiry – Mouse Party! The goal – To understand the way drugs work in the brain, and how they are able to manipulate the neurotransmitters in your brain to change the way you think. General Info: Classify all drugs as either stimulants, psychoactive or depressants. Classify each of the responses as an inhibitory or stimulatory response on the postsynaptic cell Identify the specific effects of at least two stimulants and two depressants on the nervous system Determine the factors that feed into addiction – genetic, environmental, dopamine secretion Evaluate endorphins as painkillers. Evaluate the effect of MDMA on dopamine and serotonin metabolism in the brain. Produce a chart on a sheet of paper with the answers to each of these questions on it. Click the mice for the link to the website.